Rationalism

Rationalism claims that our knowledge of the world rests on firm foundations derived from ideas that we know a priori, before experience. We have ideas or knowledge that are not merely kinds of "knowing how" (such as knowing how to suckle) but can be used in propositional knowledge - factual knowledge or "knowing that...". So, not mere instincts. Innate knowledge or innate ideas are ideas or facts we are born with, even if they require experience to realise their potential, to make us aware of them. Claims are made for the idea of God, of maths and inferential reasoning, for morality and beauty. A famous example of a rationalist's claim about innate ideas is Descartes' Trademark Argument for the existence of God: we find in ourselves the idea of a perfect being, only a perfect being could have placed that idea in our minds from birth, therefore the perfect being must exist.

Intuitions are ideas or facts that are simply self-evident - "clear and distinct ideas", Descartes called them. We grasp them by pure thought or introspection. Descartes thought that we grasp the real nature of objects in this way: not their secondary, perceptual features but their underlying measurable features (extension - mass, etc.) G E Moore, a twentienth century moral philosopher, thought the rules of morality were grasped intuitively, not by experience - they are simply self-evident.

Another kind of a priori knowledge is analytic knowledge. That is knowledge of the identity or sameness of two different ways of putting things. Analytic propositions are true by definition. So, for example, "Torture is cruel" might be considered analytic (rather than synthetic) because it is true by definition: it is built into the concept of torture that it is cruel. A lot of philosophy is about analysing concepts in this way.

In general, rationalists argue that a priori truths are necessarily true. They are not contingent on how the world happens to be: they simply have to be true, the world could not be otherwise. Empiricists claim the opposite: the only necessarily true propositions are analytic ones and they don't give us any new information about the world; they simply repeat the same thing in different terms.

Rationalists claim that it is by pure rational thought that we are able to generalize from particular instances (experiences, observations, experiments) to reach necessarily true laws of nature. We do this by maths and by ampliative inductive inference.

Criticisms of rationalism. Research these for yourself, but make sure you consider the innate, intuition and analytic points separately. Are there really any ideas or facts that are innate in every human being? God? Morality? Maths? Reasoning? Do all hmans really find the rules of morality self-evident, or grasp the underlying nature of physical objects? Is Hume right when he argues that analytic truths are not facts about the world; they are only definitions - analysing the necessary conditions for using a particular term or concept?

On the other hand, is it not true that we do need to generalise from particular instances? Repeating experiences or observations does not gives us knowledge of general principles or laws of nature> For that we need maths, logic, rules of inference (such as non-contradiction). So you might agree with rationalists to some extent - at least, that experience alone cannot give us useful, practical or scientific knowledge.